Light emitting devices, such as light emitting diodes (LEDs) and laser diodes (LDs), which use a Group III-V or Group II-VI compound semiconductor material, may render various colors such as red, green, blue, and ultraviolet by virtue of development of thin film growth technologies and device materials. It may also be possible to produce white light at high efficiency using fluorescent materials or through color mixing. Further, the light emitting devices have advantages, such as low power consumption, semi-permanent lifespan, fast response time, safety, and environmental friendliness as compared to conventional light sources, such as fluorescent lamps and incandescent lamps.
Therefore, these light emitting elements are increasingly applied to transmission modules of optical communication units, light emitting diode backlights as a replacement for cold cathode fluorescent lamps (CCFLs) constituting backlights of liquid crystal display (LCD) devices, and lighting apparatuses using white light emitting diodes as a replacement for fluorescent lamps or incandescent lamps, headlights for vehicles and traffic lights.
In the case of a light emitting device having a via hole, the thickness thereof is greater than that of a light emitting device having a semiconductor layer with a general thickness. For this reason, the length of a path, along which light generated from an active layer travels before being outwardly emitted, is long, so that the amount of light absorbed in the semiconductor layer disposed over the active layer increases. As a result, the light extraction efficiency of the light emitting device may be degraded.